WAMS-Supported Power Mismatch Optimization for Secure Intentional Islanding

Abstract

It is expected that a coordinated operation of several system integrity protection schemes will become a necessity in the future. This research represents an innovative strategy for coordinating under-frequency load shedding and intentional controlled islanding schemes for improving electric power system stability and resilience. In the great majority of real-world cases, both approaches follow conventional tactics, i.e., disconnecting a fixed number of feeders at predefined frequency thresholds and isolating a predefined area of a power system regardless of the actual conditions. Under the newly arisen network conditions in which weather-dependent distributed energy sources introduce a significant level of intermittency, conventional approaches need to be upgraded in order to retain a high level of power system operation security. In this paper, a mixed-integer linear programming approach is used to adjust the island size, including/excluding additional substations according to the available amount of generation in the region. The fine-tuning of the power rebalancing is achieved by potentially blocking selected load shedding stages. This minimizes the power imbalance of the newly formed islands, which helps to reduce the number of partial or even total blackouts and also accelerates the power system’s restoration process. The optimization approach was tested on a generic IEEE 39-bus network and shows promising results along with the capability of coping with real-world applications using wide-area monitoring systems as a source of real-time measurements. The results also indicated the importance of appropriate load modelling since both voltage and frequency dependence are recognized to have a significant effect on intentional controlled islanding.

Intentional Controlled Islanding Strategy for Wind Power Plant Integrated Systems

“…A transition of y i,k from 0 to 1 indicates the source node, and for the source node of each sub-graph, u i,k is set to 1. Flow conservation is maintained through Equation (25) with f l,k representing the amount of flow on line l of sub-graph k and q i,k representing the total consumption of the sub-graph as defined in (26). Equations ( 27) and ( 28) are a linearised form of (26) that includes a quadratic term.…”

“…However, the dynamic frequency response of islands was not considered. An approach for coordinating the ICI and existing Under Frequency Load Shedding (UFLS) was presented in [24,25]. In both [26] and [27], the frequency stability of islanding was represented by the linear frequency response of the islands, which was modelled as the average frequency response of turbine-governor and boiler models of conventional generators within each island.…”

Power System Analysis during Fast Desynchronization from Synchronous Area and Operation in Islanded Mode

“…The frequency containment reserves (FCR) and frequency restoration reserves with automatic activation (aFRR) values of the isolated EPS were calculated and simulated. The potential of HVDC to stabilize and restore the parameters of an isolated EPS were investigated [8][9][10][11][12][13][14][15][16].…”